Scandinavian countries, well-known for their extensive social welfare systems and family-friendly economic policies, took five of the top 10 spots in the list, with Iceland leading the way at No. 1.

According to the report, the Scandinavian countries scored particularly well on economic opportunity because of high labor participation rates for women, low salary gaps between men and women, and ample opportunities for women to hold leadership positions.

A key cause of that is probably the high representation of women in politics and senior management positions, allowing women to advocate for the policies that allow them to achieve equity with men, Hausmann says.

"The social policies in those countries have made it easier for women to incorporate motherhood and marriage with work," Hausmann says. The report cites policies such as mandatory paternal leave, paternal leave benefits, tax incentives, and federal programs to assist women's reentry to the work force. Paternal leave makes men as much of an economic liability as women for companies that have to absorb the costs of leave.

US breaks into the top 20

The United States broke into the top 20 this year for the first time, up from No. 31 last year. The report cites the US's strong record in education equality, particularly literacy and enrollment numbers, as well as a No. 6 ranking worldwide in economic opportunity. Political empowerment is a US weakness in the index and the lack of female representation in Congress and state government is an obstacle to implementing policy that allows women more opportunity in the workforce, Hausmann says.